1. Field of the Invention
The present invention relates to a method for formation of an impurity region in a semiconductor layer by introduction of a dopant impurity as a donor or an acceptor, and to an apparatus for introducing an impurity into a semiconductor layer.
2. Description of the Prior Art
Methods for formation of an impurity region in a semiconductor substrate include heat diffusion, epitaxial growth, ion implantation, and plasma doping.
These methods require heating at a high temperature (approximately 800-1300.degree. C.) for diffusion of impurities and electric activation of the diffused impurities.
However, such heating of the semiconductor substrate at a high temperature causes problems such as crystal defects in the semiconductor substrate, a penetration of atoms other than a dopant impurity into the semiconductor substrate, or decrease in life time of a minority carrier.
In addition, there are the problems: the depth of the impurity region is as deep as several micrometers or more; and the concentration at the surface of the impurity region cannot be controlled to make a proper concentration of 10.sup.22 atms/cm.sup.3 or lower.